Question

show that triangle ABC is isosceles if angle a =70 degree and b=40 degree

Answer 1

we know sum of all angles is 180
so 70+40+third side =180
110+third side =180
third side=70
so it is a isosceles triangle bcs two angles are equal

Answer 2

Since ABCis a isoceles trangle in which 2 angles are equal
A+b+c =180° (sum of angle of a trangle)
70+40+B=180° B=180-110
B=70°